Home » Public Forums » GMCnet » [GMCnet] Should I put a 75 or 76 distributor in my 73- 455.
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292395 is a reply to message #292387] |
Thu, 17 December 2015 19:51   |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
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BobDunahugh wrote on Thu, 17 December 2015 15:34The 73 system is simple. And are very dependable. I'm trying to convince myself to just leave it stock. I got lucky with this 73. It's in good shape as I see it now.Bob Dunahugh Member GMCMI73 GMC78 Royale4441 Deer View RdCedar Rapids Iowa319-521-4891
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Bob,
I know that you have an EFI setup getting ready to go. If you include spark control with the setup you will need an HEI or some hotrod version distributor that can use a module capable of spark control. With EFI, if I had to choose spark control or fuel control I would be hard pressed to not choose spark. Even without EBL, the GM computer is capable of spark control with knock sensor. GM knew this was the wave of the future in the early 80s.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292407 is a reply to message #292395] |
Fri, 18 December 2015 00:28 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Keep in mind you will need to put on a newer air cleaner as the old one
will hit the distributor.
Lot of people band a dent on the old cleaner, but disregard that now the
air filter will not seal properly.
On Thu, Dec 17, 2015 at 5:51 PM, George Beckman wrote:
> BobDunahugh wrote on Thu, 17 December 2015 15:34
>> The 73 system is simple. And are very dependable. I'm trying to convince
> myself to just leave it stock. I got lucky with this 73. It's in good
>> shape as I see it now.Bob Dunahugh Member GMCMI73 GMC78 Royale4441 Deer
> View RdCedar Rapids Iowa319-521-4891
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> Bob,
>
> I know that you have an EFI setup getting ready to go. If you include
> spark control with the setup you will need an HEI or some hotrod version
> distributor that can use a module capable of spark control. With EFI, if I
> had to choose spark control or fuel control I would be hard pressed to not
> choose spark. Even without EBL, the GM computer is capable of spark
> control with knock sensor. GM knew this was the wave of the future in the
> early
> 80s.
>
> --
> '74 Eleganza, SE, Howell + EBL
> Best Wishes,
> George
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292408 is a reply to message #292407] |
Fri, 18 December 2015 00:53 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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I would go with the HEI distributor ,replacement parts are still plentyful at parts stores points not so much . Easier starting then points less maintenance less chance of fouling a plug as the spark is a higher voltage. You will be a lot happier with the HEI in the long run just be sure to run a new 12 volt feed line as the points feed line has a resistor in it.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292419 is a reply to message #292387] |
Fri, 18 December 2015 09:08 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Matt if you only installed the Pertronics stand alone, would you keep the GM resistor wire? I installed one in a 69 Buick 400. I read the directions every way to Sunday and called them as well and could get no solid answer on this as to resistor or hard 12V. Right now I have retained the GM resistor wire and it seems to run fine. Idle is more steady and revs responsively, but not plated for road test. Did you drive yours W/O CD and find you needed it? So Bob, I pretty much agree wilth this route, keeping a points/cond set onboard as spares .
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292424 is a reply to message #292419] |
Fri, 18 December 2015 09:34 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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JohnL455 wrote on Fri, 18 December 2015 10:08Matt if you only installed the Pertronics stand alone, would you keep the GM resistor wire? I installed one in a 69 Buick 400. I read the directions every way to Sunday and called them as well and could get no solid answer on this as to resistor or hard 12V. Right now I have retained the GM resistor wire and it seems to run fine. Idle is more steady and revs responsively, but not plated for road test. Did you drive yours W/O CD and find you needed it? So Bob, I pretty much agree wilth this route, keeping a points/cond set onboard as spares .
John,
I did indeed keep the ballast resistance wire in the system. It is really there to allow a better starting ignition, but save the coil from over heat at idle, so it really is still needed.
It is even still there with my CDI box(s). With the CDI, I can reliably fire an 0.060 gap platinum plug. I was wanting to go to 0.080, but this lost my nerve on that one. I do have good wires and cap, but it is still the stock coil.
This is about my eighth CDI install and they always make for a more steady idle. Typically there is a small MPG boost too, but I didn't run the coach long enough without to prove that one.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292439 is a reply to message #292387] |
Fri, 18 December 2015 15:51 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Bob if she runs great now this is something you can add at a later date. You have plenty of other stuff to do. And yes, once the spark happens the event is over and the coil has dumped to ground. The voltage at which that happens depends on gap, cyl conditions, wire impedance and other conditions. I know on later distributorless ign designs, the module limits primary current to coils at low RPM to prevent heat soaking them. Once saturated adding more dwell doesn't produce more output on the secondary side.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292455 is a reply to message #292448] |
Fri, 18 December 2015 18:33 |
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Anonymous
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reliable, fewer and less spares to carry for a complete back-up ignition. the one I have has been updated to HEI which is good but I would like to have a complete points ignition set as a spare back up. couldnt hurt to have the EMP insurance that comes with a mechanical ignition either I suppose.
are the replacement points that are available worth a crap though? be nice to have irridium or platinum contacts in a set.
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292469 is a reply to message #292435] |
Sat, 19 December 2015 00:42 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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My experience when I installed hei distributors in 8:1 compression Chevy engines that were in street rods they started easier and were less apt to foul plugs. The last set of points I bought was expensive and of poor quality compared to original gm.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292512 is a reply to message #292387] |
Sat, 19 December 2015 17:44 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Another option that works pretty well is a CDI in conjunction with points. Vastly extends the points life, and can be wired to bypass it if it fails.
I have had good luck with MSD 6/6AL boxes although I know people who havent.
Re: EMP resistance: not sure how an HEI module would fare. Have heard differing opinions. Points would be best.
MSD folks claim the older [non digital] boxes are sufficiently sheilded, grounded and potted it wouldnt be an issue.
Hope we never have to find out. Just finished 'One Second after"...
76 Glenbrook
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292514 is a reply to message #292387] |
Sat, 19 December 2015 18:09 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Given the design and function of the HEI, I don't see EMP as a concern. It's already handling pulses of higher voltage and current without problems. I bought a complete HEI system with a drive gear and shaft suited to a five liter Ford V8 for less than $40 new for the Ratrod Toad a while back. A look at the one I removed makes me think the top would work just fine with a GMC shaft and reluctor and gear in place of the Ford one. Bought it off Ebay and I think it actually came from Amazon. I carry it and a spare module in case I need to do roadside upgrades.
I've been l;ooking at the FiTech injection system, whose spark control won't work with the HEI system. The FiTech people say, however, that a properly curved HEI will do as well as their spark control. For those who want a knock sensor and an injection system which takes advantage of it, the FiTech isn't the move anyway.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292515 is a reply to message #292387] |
Sat, 19 December 2015 18:18 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Bob
If you decide your going with a new distributor there are a couple of things to keep in mind. The HEI out of a car will not have a correct vacuum advance pod. The Springs and weights of the Mechanical advance are not going to be ideal. (Even stock GM coach distributors can sure use help to wake up your engine) And you MUST upgrade the wiring system Both High Voltage and Low Voltage. Here is my suggestions for upgrading the Low Voltage. Read over the entire Album of pictures including the comments. Either follow these or someone elses: but understand what your trying to accomplish.
http://www.gmcmhphotos.com/photos/g6299-hei-wireing-upgrade.html
As you can see from others postings there are other physical changes you have to make to fit that BIG distributor cap behind the Air Cleaner. Bashing in the Air cleaner to clear the distributor. (Im not sure about a point system. BUT my Air cleaner has the clearance dimple and also it is further ahead on the engine. - the air horn hole is not centered but to the rear of the Air Cleaner)
Dick Patterson at Springfield Ignition has been upgrading distributors for a long time now and many can attest to an improvement in performance. I would suggest you send yours to him first before installing it.
As an aside note to all those that might not know. HEI, PERTRONICS, and many other transistorized ignition systems Simply replace the points with an electronic triggering of the opening of points. The coils develop high voltage from a collapsing magnetic field produced during the dwell phase.(closed points developing a magnetic field) Matt Collie has been discussing a CDI. Or Capacitive discharge ignition. The CDI works opposite in that it Dumps (very quickly) a very high voltage into the coil and the coil fires on the increasing magnetic field, producing significantly higher and faster rise time voltages to the plugs. (Some do this process multiple times making a few sparks per ingition event at slower engine speeds)
Versions of CDI can be added to a point or non point system. His model of CDI is being driven (controlled by the pertronics module but the CDI is unfortunately not available in the marketplace. The PERTRONICS ignition kit is a very simple install in the point type distributor that takes the place of the points.
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292526 is a reply to message #292515] |
Sat, 19 December 2015 20:44 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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John,
You've done a good job of clarifying the ignition confusion which might
have affected some folks. One point that should be made clear: Dick
Paterson is a firm believer in the Pertronics mod; it's what he puts in
non-HEI distributors for the GMC, so he's a one-stop shop for replacement
for '73 & '74 GMCs.
Ken H.
On Sat, Dec 19, 2015 at 7:18 PM, John Heslinga wrote:
> Bob
>
> If you decide your going with a new distributor there are a couple of
> things to keep in mind. The HEI out of a car will not have a correct vacuum
> advance pod. The Springs and weights of the Mechanical advance are not
> going to be ideal. (Even stock GM coach distributors can sure use help to
> wake
> up your engine) And you MUST upgrade the wiring system Both High Voltage
> and Low Voltage. Here is my suggestions for upgrading the Low Voltage.
> Read over the entire Album of pictures including the comments. Either
> follow these or someone elses: but understand what your trying to
> accomplish.
>
> http://www.gmcmhphotos.com/photos/g6299-hei-wireing-upgrade.html
>
> As you can see from others postings there are other physical changes you
> have to make to fit that BIG distributor cap behind the Air Cleaner. Bashing
> in the Air cleaner to clear the distributor. (Im not sure about a point
> system. BUT my Air cleaner has the clearance dimple and also it is further
> ahead on the engine. - the air horn hole is not centered but to the rear
> of the Air Cleaner)
>
> Dick Patterson at Springfield Ignition has been upgrading distributors for
> a long time now and many can attest to an improvement in performance. I
> would suggest you send yours to him first before installing it.
>
> As an aside note to all those that might not know. HEI, PERTRONICS, and
> many other transistorized ignition systems Simply replace the points with an
> electronic triggering of the opening of points. The coils develop high
> voltage from a collapsing magnetic field produced during the dwell
> phase.(closed points developing a magnetic field) Matt Collie has been
> discussing a CDI. Or Capacitive discharge ignition. The CDI works opposite
> in
> that it Dumps (very quickly) a very high voltage into the coil and the
> coil fires on the increasing magnetic field, producing significantly higher
> and faster rise time voltages to the plugs. (Some do this process multiple
> times making a few sparks per ingition event at slower engine speeds)
>
> Versions of CDI can be added to a point or non point system. His model of
> CDI is being driven (controlled by the pertronics module but the CDI is
> unfortunately not available in the marketplace. The PERTRONICS ignition
> kit is a very simple install in the point type distributor that takes the
> place of the points.
>
>
>
> --
> John and Cathie Heslinga
> 1974 Canyonlands 260
> 455, Manny tranny and 1 ton, 3:70 LS,
> Red Seal Journeyman, DTE, BEd. MEd.
> Edmonton, Alberta
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Should I put a 75 or 76 distributor in my 73- 455. [message #292529 is a reply to message #292387] |
Sat, 19 December 2015 22:01 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Thanks Ken.
Like you say: (Matt and others too) that pertronics upgrade is quite good and simple. It gets rid of the points in the ignition system and easy to upgrade. Ive used it in my boat, customers cars, and my Onan. Older classic cars of my friends and customers with points have found that even though they have been stored inside(cold) the point surfaces get slightly corroded or frosted. They needed cleaning in the spring to have them run right. (My boat with 5 liter ford needed this every spring because of the condensation conditions) The pertronics modules made the engine look period and same as stock. But the point problems went away and customers felt better performance. (Plus 1 less maintanance item)
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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